Process for producing colored photographic contrasts



June 12, 1956 c. J. DlPPl-:L ETAL 2,750,292

PROCESS FOR PRODUCING COLORED PHOTOGRAPHIC CONTRASTS Filed May 22, 1951 2 Sheets-Sheet 1 INVENTORS F. CORNELIS JOHANNES DIPPEL 7 HENDRIK JONKER BY ,s/1MM AGENT June l2, 1956 c. J. DIPPEL ETAL 2,750,292

PROCESS FOR PRODUCING COLORED PHOTOGRAPHIC CONTRASTS Fi', INVENToRs HENDRIK JoNKER CORNELIS JOHANNE DIPPEL Y @(MENT United States Patent O PRCESS FR PRQDUCING COLORED PHOTGRAPHHC -CQNTRASTS Cornelis Johannes Dippel and Hendrik donker, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Enna., as 4trustee Application May Z2, 19151, Serial No. 227,564

Claims priority, application l'alethelnnds vMay 26, 1950 14 Claims. (Cl. 95-88) The invention relates to a process for producing coloured photographic contrasts.

Coloured photographic contrasts have heretofore been produced by exposing a light-sensitive system to the action of light having a given spectral distribution l.followed by developing the resulting light-decomposition product formed upon exposure to a contrast of desired colour or to a contrast which is subsequently converted into the corresponding colour by causing dyestuffs to form a coloured contrast yon the film.

According to the invention, the formation of the dye contrast takes place simultaneously and in situ with the formation Yof' the metal contrasts during physical development. The metal may or may not be then removed as desired.

The invention-makes use of a developing process known as physical development as distinguished from chemical development, the metal required for contrast vformation being largely supplied from the developer whereas in chemical development the metal required for contrast formation being available only from the metal ions in the crystal lattice of the grains on the film.

Latent images formed by -the reaction of a light-de composition product with a metal salt from the group consisting of mercury, silver, gold and platinum in this manner provide suitable contrasts for producing coloured images by physical colour development. All known standard dye-formations may be employed in physical colour development. The dye-formationmayor may `not take place in coaction with a colour coupler.

Moreover, itis possible by means of the foregoing development to expose the film sequentially to light of rdifferent spectral distributions to form twoor three-colour images. After each exposure the ilm is developed and dyed a corresponding colour.

The coloured photographic contrasts produced by the process according to the invention are extremely sharp, deep-coloured, and substantially free from fog.

The invention will be described with reference to the accompanying drawing in which-- Fig. 1 shows a colour filter for making twoand threecolour photographs;

Fig. 2 shows a colour of the film;

Fig. 3 shows the formulae of the various dyestui forming compounds referred to in the specificationand the following examples:

grating obtained after exposure Example I A lm consistingof superfcially saponied cellulose acetate is sensitized by immersing it in an aqueous solution containing 5% of mercuric chloride 5% of ferrie ammonium oxalate and 2.5% of ammonium oxalate The adhering liquid is Vremoved and lthe 'film is dried. After a strip of the lm has been exposed under a trans- 2,750,292 Patented `lune 12, 1956 parent negative by means of a mercury vapour lamp and rinsed in distilled water for a few minutes, it is treated for 15 minutes with an aqueous solution containing 0.1% o f thio'indoxyl (Formula I) (Fig. 3) 0.2% n ammonia and 0.4% of silver nitrate A latent amalgam image is formed, which is developed further, a dye image being obtained in situ with the amalgam image. The developed tilm is washed, whereupon the metal image may be dissolved, for example .by means of a liquid containing potassium ferricyanide and a .thiosulphate, a fog-free, positive, red dye image being obtained. Finally the iilm is washed in running water.

The use of indoxyl (Formula il) `instead of thieindoxyl Vyields a blue dye image. Colour development for 20 minutes in a physical developer containing:

0.15% yof-phenylhydrazone of glyoxylic acid amide .(Formula III) 0.25% `of sodium hydroxide 0.4 ,n.amrnonia and 0.4% of silver nitrate in ywater Yields Ia yellow `dye image.

In a preferred embodiment of the method according to the invention the colour formation takes place with the aid /of a colour coupler during the `physical development. This form olfers a large variety of possibilities of obtaining the desired colour shade.

The dye forming component Ymay be incorporated in the sensitized layer of the photographic material used as a starting point for the method according to the invention. If the dye forming component is incorporated in the sensitized layer it should be sufficiently fast to diffusion. Methods of rendering dye forming components fast to diffusion are known, the choice of the dye forming component being also determined by considerations .of a general practical nature. Thus, for example, it isessential that the dye forming component which is to be incorporated in the layer must not be detrimental to the reaction of light and must not have a disturbing effect in some other respect.

In certain cases, for example in connection with the disturbing activity of the dye forming component when present in the layer together with the light sensitive sys tem, it may be desirable to introduce a.dye forming component into the layer by means of a solvent and by a separate treatment between exposure and development, which component may dissolve to an insuliicient degree inthe `developer but otherwise may have advantageous properties.

Example II Astrip .of film of the same type as used in Example I is lsoaked in succession, after exposure and washing, in an aqueous solution of 2% of pentabrom-2,3,4,6,7 naphthol-l (Formula IV) and 0.3% of sodium hydroxide and in a 0.2 n solution of sulphuric acid in water. After washing, the film is treated for 5 minutes with a colour forming physical developer, containing 0.08% of stabilized colour developer having p-diethylaminoaniline (Formula XXXI) as the active component and marketed by May and Baker under the registered trademark of Genochrome 0.5% of sodium thiosulphate 0.2 n ammonia and '0.4% of silver nitrate in distilled water After ,removal of the metal image ka .green dye image is obtained.

For practical reasons the dye forming component will frequently be dissolved in the developer. This permits the use of less complicated and consequently cheaper dye forming components, while there are sufficient possibilities of obtaining the desired colour shade.

Example III After exposure and Washing a strip of lm of the type used in Example I is treated for 20 minutes with an aqueous solution containing 0.15% of Z-phenylsemicarbazide (Formula V) 0.25% of sodium hydroxide 0.1% of naphthol-2 (Formula VI) l n ammonia and 0.4% of silver nitrate After removal of the metal image an orange dye image is obtained.

It has been found that, besides physical developers containing a soluble silver compound, it is also possible to use developers containing a compound of a different noble metal, including mercury. In another embodiment of the method according to the invention the physical colour forming developer contains a soluble mercury compound as a metal compound. In general, these developers have the advantage over the developer containing silver compounds that they are more stable for an equivalent developing effect. Moreover, it is advantageous that physical colour forming mercury developers are serviceable in the weekly acid pH-range, whereas corresponding silver developers have serious limitations in this respect, which is of importance in view of the conditions of formation and/or the stability of particular dyes.

Example IV After exposure and washing, another strip of the film of the type used in Example I is brielly dipped in a 2 n aqueous solution of ammonia and physically colour-developed for minutes in a mixture of 25 ccs. of an aqueous solution containing 0.2% of Genochrome (Example II) 3% of sodium carbonate (water free) 3.5% of potassium thiocyanate and 0.7% of mercurio bromide and 1 ccm. of solution of 2% of phenyl-l methyl-3 pyrazolone-5 (Formula VII) in ethanol.

After the removal of the mercury image a magenta dye image remains. Similarly to the solutions of Example II, this solution has a vigorous developing effect and a high degree of stability.

Example V A lm consisting of regenerated cellulose is sensitized by soaking in an aqueous solution containing 0.4 n hydroxy-l diazonium-2 methyl-6 benzenesulphonic acid-4 and 0.1 n mercurous nitrate.

The dried film is exposed under a transparent negative by means of a mercury vapour lamp and immersed immediately after that in a physical colour forming developer obtained by mixing 25 ccs. of an aqueous solution of 0.08% of the nitrate salt of the compound dimethyl-l amino-4 phenylamine (Formula VIII) 0.09 n nitric acid and 0.024 n mercurous nitrate and 1 ccm. of an alcoholic solution of 10% naphthol-l (Formula IX). The duration of the development is minutes. A mercury image in situ with a dye image are obtained. The positive bluish-green dye image is insulated by removal of the mercury image, for example in the solution referred to in Example I.

The pI-I value of the developer should preferably be made smaller than 7 if this condition is consistent with the rapidity of the colour forming reaction, with the solubility of the dye forming component and with the stability of the desired dye. This choice has the advantage of obtaining fog-free dye images and in addition the dyes produced generally have a lower degree of solubility. Moreover, it has been found that the stock solution for such a developer, which consequently does not contain a noble metal compound, is much stabler than the stock solution of a corresponding chemical colour developer.

Example Vl A leaf of unsized paper is sensitized by soaking it, for example, in the solution referred to in Example V. After exposure of a piece of the dried paper it is briefly washed in distilled water and subsequently colour-developed for 5 minutes in a physical developer obtained by mixing 25 ccs. of an aqueous solution of 0.08% of ethylbenzylamino 4 (Formula X) 5% of tartaric acid and 0.4% of silver nitrate and 3 ccs. of a saturated aqueous solution of dimethylamino-l-acetylamino-3 benzene (Formula XI).

This yields a metal image in situ with a green dye image. After removal of the silver and treatment for a few minutes with an aqueous solution of 2.5% of phosphotungstic acid a violet red dye image is obtained.

Example VII A film consisting of regenerated cellulose is sensitized by soaking for 2 minutes in an aqueous solution of 0.2 n silver nitrate, followed by soaking for one minute in a 2 n potassium bromide and 0.5 n nitric acid aqueous solution. Before use, the last-mentioned solution is briefly warmed to boiling temperature and cooled, the lm being subsequently rinsed in running Water and dried.

A strip of the film is exposed under a transparent negative by means of an electric incandescent lamp and subsequently treated for 3 minutes with a physical colourdeveloper obtained by mixing 25 ccs. of an aqueous solution of phenylamine nitrate 0.08% of nitrate salt of the compound dimethylamino-4 phenylamine (Formula VIII) 5% of tartaric acid and 0.4% of silver nitrate and 1 ccm. of a solution of a dye-forming component, for example that used in Example IV.

After fixation of the images in a neutral or alkaline fixing bath and removal of the silver image, a strong magenta dye image is obtained. Another strip of the same film is exposed under a sensitometer and colour-developed for 10 minutes in a physical developer obtained by mixing 25 ccs. of an aqueous solution of 2% of the sulphate salt of the compound (hydroxy-4 phenyl) methylamine (Formula XII) 4% of tartaric acid 0.4% of silver nitrate and 2.5 ccs. of an alcoholic solution of 10% naphtol-l (Formula IX). A dark-brown dye image is obtained in situ with a black-silver image, the contrast being materially increased by the dye image.

Example VIII A piece of the sensitized paper of Example VI is exposed, briefly rinsed and developed for 6 minutes in a physical colour-forming developer obtained by mixing 25 ccs. of an aqueous solution of 2% of benzenediol-1-4 (Formula XIII) 1% of lactic acid and 0.4% of silver nitrate and 3 ccs. of a 2% phenol alcoholic solution (Formula XIV). A dark brown dye image is obtained in situ with a black metal image as a result of which the contrast is much stronger than if the solution of the dyeforming component is not added. The `addition .of rsolutions ofmany of other `phenols, phenylamines, naphthols or naphthylamines to the ph fsical .benzenediol-developer have the same eifect.

Example IX Example X Cellulose acetate saponitied at the surface is sensitized by soaking it in an aqueous solution ycontaining 0.02% of methylene blue. The greenish blue iilm Yabsorbs red light but is substantially transparent to -blue and 1green rays. Exposure is effected under a transparent Knegative by means of an electric incandescent lamp. After exposure it is treated for half a minute with a 1% silver nitrate solution in water, followed by rinsing the dye vout of the lm. Subsequently, the film is colour-developed for 6 minutes to a greenish blue tone by means of the physical dimethyl-amino-4 phenylaminenitrate developer of Example VII to which double the quantity of a solution of naphtol-l in ethanol is added instead of l com. of a Vpyrazolone solution. The silver image is .removed as indicated and a positive dye image is obtained.

If, in connection with the character of the colourforming reaction and the properties of the dye forming component and the dye it is necessary for the pH-value of the developer to be chosen to exceed 7, it will be necessary, because of practical considerations in choosing the agent forming complexes together with the noble metal compound and in determining the concentration of this agent, to allow for a possible disturbing influence of the said agent on the colour formation.

of cellulose acetate saponied at the surface in an aqueous solution of ferrie-ammonium oxalate or citrate and silver- .nitrate is exposed, brielly rinsed in distilled water and colour-developed for l0 minutes in a physical developer obtained by mixing 25 ccs. of an aqueous solution containing 0.08% of Genochrome (Example II) v0.5% of sodium thiosulphate v0.2 n ammonia and 0.4% of silver nitrate and 3 ccs. of a 0.8% solution of aceto-ace't (dichlor-'2.5) anilide (Formula XVI) in acetone. After removal o'f the metal a beautiful yellow dye image is obtained.

Example XII The following stock solutions for colour-formingphysical developers are prepared:

A. 3% of sodium carbonate (water free) 3.5% of potassium thiocyanate and 0.7% of mercuric bromide in distilled water.

B. 10% of Genochrome (Example Il) in distilled 'water C1. 2% of hydroxy-l methyl-2 dibrom-3.5 benzen (Formula XVII) in ethanol C2. 2% of rhydroxy-1 dichlor-2.4 naphthalene (Formula XVIII) in ethanol C3. 5% of hydroxy-1 thioglycollylamino-Z Chlor-4 methyl-5 benzene (Formula XIX) and 0.5 n sodium hydroxide in water After exposure for 5 minutes several strips of a sensitized film, for example of the film referred to in Example l, vare colour-developed in physical developers obtained by mixing 25 ccs. of solution A, 0.5 ccm. of solution B and l cmof solution C1 or C2, or-0.3 ec. of solution C3. The addition of solution C may alternatively be replaced by the admixture of 25 mgms. of hydroxy-l naphthalenesulphonic acid-4 (Formula XX). After removal of the metal images green and greenish blue dye images are obtained. The following stock solutions are also prepared:

C4. 1% of (nitro-4 phenyl) acetonitrile (Formula XXI) in methanol C5. 5% of phenyl-l thioglycollylamino-3 pyraZolone-S (Formula XXII) and 0.5 n sodium hydroxide -in water Cs. 2% of acetylacetonitr'ile (Formula XXIII) in acetone C7. 2% of phenylacetonitrile (Formula XXIV) in methanol Ca. 2% of ethylacetylacetate (Formula XXV) in methanol C9. 2% of ethyl-benzoylacetate (Formula XXVI) in methanol Cin. 2% lof aeetylacetone (Formula XXVII) in methanol C11. 2% of ethyl-acetylchloracetate (Formula XXVIII) in methanol C12. 5% benzoylacetoamino-l-1 benzenesulphamide-4 thiephenol (Formula XXIX) and V0.5 n sodium hydroxide in water Physical colour-forming developers for magenta-coloured images are obtained by admixture of l ccm. of the solution C4 or 0.3 ccm. ofthe solution C5 to a mixture of `25 ccs. of solution A and 0.5 ccm. of solution B. Physical developers yielding yellow to yellowish-browndye images are obtained by the admixture of l ccm. of the solutions Cs or C7, Cs, C9, Cio, C11 or of 0.3 ccm. of the solution C12.

VThe method according to the invention may be used for silver halide material and then has the aforesaid advantages. However, it has the particular advantage that it may also be used for other systems, for example those which are based on the light-sensitiveness of diazo compounds for which the chemical colour-forming development cannot be used directly. In the last-mentioned case, in effect, the high resolving power inherent in `these systems and the tine grains obtained by physical development, can be utilized to full advantage. With the use of the method according to the invention for these systems it is readily possible to produce dye images having a resolving power of 700 lines per millimeter. In copying, this high resolving power permits, if desired, a considerable reduction of the image size. In this case, it is also possible to utilize the property that the characteristic curve of the dye image gradually rises during development and does not bend over at higher optical densities. This permits highly saturated colours to be o btained.

Consequently, the method according to the invention permits the production of'images in one colour in paper, regenerated cellulose, wood, glass and so when sensitizing these materials, `for example by incorporating ka diazocompound with the aid of a simple soaking technique. In this event the aforesaidphysical developers containing a soluble mercury compound have vthe additional advantage that they may also serve to form the latent metal contrast, so that a separate treatment for the formation of this image is superfluous. '1n this case the material need not contain a mercury compound. The method according tothe invention permits, for example, the production of developing photoprinting papers in a variety of colours, which are much more ysensitive than the conwhich are often 'faster to light.

7 Example XIII The following stock solutions for colour-forming physical developers are constituted:

A1 0.08% of amino-4 phenylaminenitrate (Formula XXX) and of tartaric acid in water A2 0.08% of dimethylamino-4 phenylaminenitrate (Formula VIII) and 5% of tartaric acid in Water A3 0.08% of diethylamino-4 phenylaminenitrate (Formula XXXI) and 5% of tartaric acid in water A4 0.08% of ethylbenzylamino-4 phenylaminenitrate (Formula X) and 5% of tartaric acid in water A5 0.08% of methylhydroxyethylamino-4 phenylaminenitrate (Formula XXXII) and 5% of tartaric acid in water As 0.08% of ethylhydroxyethylamino-4 phenylaminenitrate (Formula XXXIII) and 5% of tartaric acid in Water Afr 0.08% of amino-4 phenylglycine-Na XXXIV) and 5% of tartaric acid in water Aa 0.2% of dimethyl-3, 3 diamino 4, 4 diphenyl (tolidine) (Formula XXXV) and 5% tartaric acid in water A9 0.6% of hydroxy-4 phenylamine (Formula XXXVI) and 1.5% of lactic acid in water B1 2% of naphtol-l (Formula 1X) in ethanol B2 2% of dihydroxy1.5 naphthalene (Formula XXXVII) in ethanol B3 2% of amino-l naphthalene (Formula XXXVIII) in ethanol B4 2% of hydroxy-8 quinoline (Formula XXXIX) in ethanol B5 2% of amino-3 phenol (Formula XXXX) in ethanol B6 2% of dimethylamino-3 phenol (Formula XXXXI) in ethanol B7 2% of thioindoxyl (Formula I) in ethanol Bs 2% of phenyl-l methyl-3 pyrazolone-S (Formula VII) in ethanol C 10% of silver nitrate in water.

(Formula Unsized paper is sensitized by soaking it in an aqueous solution of a diazo-compound and mercurous or silver nitrate. After exposure, images are produced in different colours on pieces of this paper by physical colour-development for 5 to 10 minutes. Different colour-developers are constituted by mixing a stock solution A, a stock solution B and a stock solution C. For example:

(a) 25 ccs. of solution A1 or A2, As, A4, A5, As, 3 ccs. of solution B3 and 1 ccm. of solution C. After removal of the metal images, dye images in violet shades are obtained.

(b) 25 ccs. of solution A2 or Aa, A4, As, As, 3 ccs. of solution B1 and 1 ccm. of solution C. After removal of the metal images blue dye images are obtained.

(c) 25 ccs. of solution A4, 3 ccs. of solution B2 and 1 ccm. of solution C. Bluel dye image.

(d) 25 ccs. of solution A4, 3 ccs. of solution B4 or Bs, Bs and l ccm. of solution C. Dye images in greenishblue shades.

(e) 25 ccs. of solution A1, 3 ccs. of solution Bi or B2 and 1 ccm. of solution C. Purple or red dye image.

(f) 25 ccs. of solution A4, 3 ccs. of solution B1 or Bs and l ccm. of solution C. Magenta dye images.

(g) 25 ccs. of solution A7, 3 ccs. of solution Bi or B2, B3 and 1 ccm. of solution C. Dark pink to red shades.

(h) 25 ccs. of solution As, 3 ccs. of solution B1 or B2 and 1 ccm. of solution C. Magenta shades.

Example XIV Paper is sensitized by soaking it in an aqueous solution of 2% of methyl-l Chlor-2 benzenediazosulphonic acidsodium-4. A strip of the dried paper is exposed under a transparent negative by means of a mercury vapour lamp. The latent mercury contrast is formed by immersion in the physical colour developer of Example V, this contrast being developed with the simultaneous formation of a positive dye image after continued stay in the said developer.

A promising use of the method according t'o the invention is in the eld of textile printing, since photographic images in cotton, artificial silk, silk and so on can be produced in a single manner with the use of the aforesaid sensitization technique.

Example XV A white cotton handkerchief is sensitized by soaking it in an aqueous solution containing 0.2n hydroxy-1 diazonium-Z methyl-6 benzene sulphonic acid-4 0.2n mercurous nitrate and 0.2n nitric acid and dried. The handkerchief is subsequently exposed behind a photographic negative by means of a mercury vapour lamp. After rinsing in distilled water it is colourdeveloped for 10 minutes in a physical developer obtained by mixing 25 ccs. of

0.08% of the nitrate salt of the compound amino-4 phenylamino (Formula XXX) and 5% of tartaric acid in Water 1 ccm. of 10% of silver nitrate in Water and 1 ccm. of 2% dihydroxy-1.5 naphthalene (Formula XXXVII) in ethanol.

The metal image is removed after rinsing. The red positive image is again rinsed and ironed to dryness between two cloths by means of a smoothing iron. The image may be washed with impunity in warm soap suds.

The method according to the invention may be used for producing images in more than one color, for example according to the so-called subtractive method and in addition for making color gratings for use in the so-called additive method.

In the first-mentioned case separation negatives or color extracts may be started with. From each of these partial negatives the corresponding colored positives are made by means of the method according to the invention, the partial images being made in register or arranged in register by superposition. If desired, one of the images may be gray. In a further preferred embodiment of the method according to the invention, differently coloured images are provided in succession in a single layer by successive sensitization, exposure and development. This is advantageous since the images extend substantially in one plane. Naturally, the sensitization necessary for each image should not adversely affect existing images.

It must be borne in mind that existing images may affect the formation of further images. rI`his may cause changes in the colors of the resulting total image, which changes may be undesirable, fo-r example when it is intended to reproduce natural colors. In this respect, reference may be made to the disturbance due to absorption of light by existing images. In order to avoid this disturbance, the existing metal image is dissolved and, according to a further feature of the invention, light of the type transmitted by the existing dye images is used for the production of each image. In addition to visible light it is possible to use ultra-violet or infra-red rays. Furthermore, it is pointed out that the metal image produced on forming each partial image is amenable to further color-development in following colors. This also may be a reason for rendering these metal images unarnenable to further color-forming development for the following sensitization.

Example XVI A film consisting of cellulose acetate saponied bilaterally at its surface (saponied layers approximately 10/p. thick) is sensitized by incorporating in the saponified layers an aqueous solution containing, for example, 0.4 n of the diazonium compound of Example XV and mercurous nitrate.

.fAt both.sides,.separation negatives are copied in register by tmeans of a mercury vapor lamp, followed by rinsing the `film in distilled water. Subsequently, one side of .the lm is developed by means of a normal physical developer, for example a metal-citric acid developer. A black metal image is obtained, which is converted into a Prussian v.blue image in a well-known manner. After that the =iilm is developed on its other side by :means of ,a color-.forming physical developer with the co-action o-f one or more dye-.forming components (previous examples), for the formation of a red-dye image in situ with v.a metal image. Finally, this metal image is vremoved in the above-described manner, the ultimate result being a .positive imagein two colors.

rOne ofthe partial positives may be vmade by means 4of any of the well-'known.toning, mordanting and similar processes, .starting witha met-al image obtained by normal physical development. In general, however, direct physical .colorfforming development of all partial positives is .to be .preferred because of its simplicity.

Example XVII Paper is `sensitized by soaking it in an aqueous solution containing 0.2 n hydroxy-l diazonium-2 methyl-6 benzenesulphonic acid-4 and 0.1 n mercurous nitrate.

The dried paper is exposed behind a green color extract. .After a short wash in distilled water the paper is color-developed for 6 minutes in a physical developer containing 0.08% of.amino4 phenylamine (Formula XXX) .5 V.of tartaric ,acid

0.4% of silver nitrate in distilled water.

'To Al00fccs. of this developer, 4 ccs. of a solution of 10% of naphtol-l (Formula IX) in Aethanol are added.

After rinsing, the metal image, for example as stated in Example I, is removed and )a purple partial image is obtained.

After Washing and drying the paper is again sensitized `by soaking it in the aforesaid solution, the exposure To 100 ccs. 4 ccs. of the aforesaid naphtol-.l solution .are again added.

As an alternative, color-development may take place in the physical developer: 25 ccs. of 'solution A4, 3 ccs. of

:solution B4,l ccm. of solution-C(Example XIId).

`Afterremovahof the metal image, anpurple and a-blue to greenish blue partial image is obtained.

YAfter washing and drying the paper is sensitized for the third time by soaking in -an aqueous solution containing 0.2 n hydroxy-l diazonium-2 methyl-6 benzenesulphonic acid sodium-4.

This time the exposure takes lplace behind a blue colour extract. `(A latent contrast is formed at the exposedareas by .means of a solution of 0.001 n mercurous nitrate in distilled water.)

Colour-,development takes place for 6 minutes in the developer of Example IX. After removal of the metal image, the yellow partial image is also present. After washing and drying the positive image is ready 'in three colours. 'The exposures are effected by means of a mercury vapour lamp. In order to ensure that the subtractive partial positives are in register, the images, in carrying out the method according to this example, are preferably produced in a thin layer adhering to a satisfactorily moisture-proof carrier `(for example .cellulose -triacetate) and intense drying of the layer .takes place only after the last partial image has been processed.

vIn producing coloured images according to the addiit? tive method, .the method according to the Yinvention is usedffor making colours gratings. This permits -making gratings both with irregular and regular colours mosaics, the .latter .having these advantages in Yaddition to those which the known gratings of this type have. In connection with the progress of the art made in the iie'ld of tine-,grained and grain-free light-sensitive systems it is of importance to note that the method according tothe invention permits the production of gratings in which at least one of the linear dimensions of the lgrating elements is very small. Only the use of such gratings permits the considerable resolving power of these light-sensitive materials to materialize also with multicolourimages produced according to the grating technique. Thus, for example, the use of physical colour-development according to the invention in the light-sensitive diazonium compound system permits the production of acolourgrating in which one of the linear dimensions of the dierently coloured elements is l/p. The hitherto known techniques do not permit the production of gratings having .such

dimensions.

Example XVIII A lilm consisting of cellulose triacetate saponified at the surface is sensitized by soaking in an aqueous solution of 0.4 n hydroxy-1 diazonium-2 methyl-6 benzenesulphonic acid-4 and 0.1 n mercurous nitrate. It appears that this `light-sensitive material, upon colour-forming physical development by means of developers referred to in Example VII, for example 25 ccs. of A1, 3 ccs. B2, l ccm. C or 25 ccs. A2, 3 ccs. B1, l ccm. C, reproduces 700 sharply separated lines per mm. in red or blue colour.

VIn such material, a colour grating can beproduced by lbe imagined in which colour gratings may be lmade by means of the method according to-the invention. Naturally, the grating may be used both for an additive reversal process and for a negative-positive process.

While the invention has been described in connection with specific embodiments other substitutions and modifications will appear obvious to those skilled in the art without departing from the spirit and scope-of the invention as defined in the appended claims.

What we claim is:

l. A method of' producing a color photographic contrast which .comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo -compounds, ferric vammonium oxalate, -ferric ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold 'and platinum to produce a latent image ofone of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consistingof mercury, silver, gold and platinum and an organic reducing agent capable 'of reducing said salt to metal while forming an oxidation product which yields an insoluble organic dye contrastsimultaneously in place with a metal contrast.

2. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, Vt'erric ammonium oxalate, ferrie ammonium 'citratevand methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a.

metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product Which yields an insoluble organic dye therely yielding an insoluble organic dye contrast simultaneously in place with a metal contrast.

3. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, ferric ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image, in the presence of a color coupler, a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product which couples with said color coupler to form an insoluble organic dye thereby yielding an insoluble organic dye contrast simultaneously in place with a metal contrast.

4. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, ferric ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a color coupler, a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product which couples with said color coupler to form an insoluble organic dye thereby yielding an insoluble organic dye contrast simultaneously in place with a metal contrast.

5. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo cornpounds, ferrie ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a color coupler and then applying a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal while forming an oxidation product which couples with said color coupler to form an insoluble organic dye thereby yielding an insoluble organic dye contrast simultaneously in place with a metal contrast.

6. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, ferric ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution having a pH of less than 7 and containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

7, A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, ferric ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible mercury salt and an organic reducing agent capable of reducing said mercury salt to mercury while forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

8. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo cornpounds, ferrie ammonium oxalate, ferric ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible silver salt and an organic reducing agent capable of reducing said silver salt to silver While forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

9. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazoniurn compounds, diazo compounds, ferric ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal while forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place With a metal contrast, and dissolving the metal contrast to leave only a color contrast.

l0. A method of producing a color photographic contrast which comprises exposing to a given portion of the spectral range selected portions of a layer containing a light sensitive compound selected from the group consisting of diazonium compounds, diazo compounds, ferrie ammonium oxalate, ferrie ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a Water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

ll. A method of producing a multicolored photographic contrast which comprises exposing portions of a layer containing a light sensitive compound selected from the group consisting of diazoniurn compounds, dazo compounds, ferrie ammonium oxalate, ferric ammonium citrate and methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal While forming an oxidation product which yields an insoluble organic dye contrast simultaneously iu place with a metal contrast, and dissolving the metal contrast to leave only a color contrast and then treating said layer with an additional amount of one of said light sensitive compounds and then exposing the layer and repeating the steps of the claim to form a second color contrast and a second metal contrast and then dissolving said second metal contrast.

12. The process of claim 11 in which the steps are repeated for different portions of the spectral range.

13. A method of producing a color photographic contrast which comprises exposing portions of a layer containing a light sensitive diazonium compound, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, silver, gold and platinum and an organic reducing agent capable of reducing said salt to metal while forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

14. A method of producing a color photographic contrast which comprises exposing portions of a layer containing methylene blue, treating the exposed layer with moisture in the presence of a water soluble salt of a metal selected from the group consisting of mercury, silver, gold and platinum to produce a latent image of one of said metals, and applying to said latent metal image a developing solution containing a reducible salt of a metal selected from the group consisting of mercury, slver, gold and platinum and an organic reducing agent capable of reducing said salt to metal while forming an oxidation product which yields an insoluble organic dye contrast simultaneously in place with a metal contrast.

References Cited in the le of this patent UNITED STATES PATENTS 1,375,659 lllig Apr. 19, 1921 1,744,642 Konds Jan. 21, 1930 1,794,693 Ippers Mar. 3, 1931 1,933,789 Crabtree et al. Nov. 7, 1933 2,067,690 Alink et al. Jan. 12, 1937 2,083,285 Alink June 8, 1937 2,150,834 Holst et al. Mar. 14, 1939 2,178,771 Alink et al. Nov. 7, 1939 2,183,447 Dippel et al Dec. 12, 1939 2,495,000 Hanford Jan. 17, 1950 2,497,917 Stauifer Feb. 21, 1950 2,553,500 Harsh May 15, 1951 2,622,025 Waller et al Dec. 16, 1952 FOREIGN PATENTS 873,507 France Mar. 23, 1942 53,515 France July 16, 1945 (4th addition to No. 873,507) 629,656 Great Britain Sept. 26, 1949 

1. A METHOD OF PRODUCING A COLOR PHOTOGRAPHIC CONTRAST WHICH COMPRISES EXPOSING PORTIONS OF A LAYER CONTAINING A LIGHT SENSITIVE COMPOUND SELECTED FROM THE GROUP CONSISTING OF DIAZONIUM COMPOUNDS, DIAZO COMPOUNDS, FERRIC AMMONIUM OXALATE, FERRIC AMMONIUM CITRATE AND METHYLENE BLUE, TREATING THE EXPOSED LAYER WITH MOISTURE IN THE PRESENCE OF A WATER SOLUBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF MERCURY, SILVER, GOLD AND PLATINUM TO PRODUCE A LATENT IMAGE OF ONE OF SAID METALS, AND APPLYING TO SAID LATENT METAL IMAGE A DEVELOPING SOLUTION CONTAINING A REDUCIBLE SALT OF A METAL SELECTED FROM THE GROUP CONSISTING OF MERCURY, SILVER, GOLD AND PLATINUM AND AN ORGANIC REDUCING AGENT CAPABLE OF REDUCING SAID SALT TO METAL WHILE FORMING AN OXIDATION PRODUCT WHICH YIELDS AN INSOLUBLE ORGANIC DYE CONTRAST SIMULTANEOUSLY IN PLACE WITH A METAL CONTRAST. 